Modern magnetic induction machines (e.g. motors and generators) primarily operate using rotating magnetic fields created by alternating current (AC), a technology that was first developed by in the late 1890's and which has been deployed universally for well over a century. Magnetic induction machines can operate based on the interaction of a plurality of magnetic fields, typically created by copper coils carrying current and/or permanent magnets and shaped using steel laminations, that are used to create force, torque or energy. In the century since its introduction, there have been many improvements to the magnetic machine, including copper and steel processing refinements, and the development of copper rotors and high strength rare-earth magnets, which may have been developed to improve efficiency characteristics, but which have also resulted in extra material processing. For this reason, many modern improvements can also increase manufacturing costs. After a century of development, magnetic machines may have reached their cost-performance limits.
In the late 1890's there was another magnetic field technology based on direct current (DC) promoted by Thomas Edison. As is commonly known, Edison's DC technology did not prevail commercially primarily because there was no economical method at the time to efficiently generate and transmit DC power over long distances.
In the century since Edison, the ability to generate and transmit DC power has advanced and the economics of transmitting high voltage DC (HVDC), which can be more efficient to transmit than high voltage AC (HVAC) because reactance in a DC system is minimized, has been shown to be beneficial for certain applications. However, usage of HVDC is relatively rare because the cost remains prohibitively high in most cases. These higher costs can be due to an increased number of conversions that are required for creating, transmitting and distributing HVDC as shown in FIG. 1, illustrating a prior art wind system for generating HVDC power. These conversions can be required because the source of the power is generated from AC magnetic machines, which necessitate the conversion from AC to HVDC then back to AC. The costs can include fabricating and installing HVDC converter stations; one to convert AC to HVDC and another to convert HVDC back to AC, which are based on specialized, electrically isolated semiconductor switches. Because of these costs, HVDC power has typically been used for applications requiring long-distance transmission runs or operation in challenging environments such as offshore wind farms where the improved efficiency, or other benefits from HVDC, can justify the added expense.
Nearly a century before magnetic field machines were developed, another machine technology based on electric fields was created. Just as the north-south magnetic fields of two magnets can create attractive and repulsive forces, electric fields from positive-negative charges can also create attractive and repulsive forces. For example, in 1784 Benjamin Franklin experimented with this electric field technology by building a spark-gap motor that placed electrical charges, via a charge transfer process, on thimbles attached to a wheel to create attractive-repulsive forces, causing the wheel to rotate, as described in O. Jefimenko, D. Walker, Electrostatic Motors, Physics Teacher, March 1971. Franklin considered his device a novelty, and nothing more, as he lacked understanding of its potential.
The origin of the electric field is the static charge, which has an inherent or innate electric field. Machines based on electric field technology (EFT) utilize this inherent electric field of static charges (i.e. electrons) for creating force, torque or energy. In contrast, magnetic field machines use current, which is the name given to charge that is in motion, to induce magnetic fields from which force, torque and energy can also be created. While electric and magnetic field machines can both create useful results, modern large power electro-mechanical machines, such as those above 100 Watts, tend to be exclusively based on magnetic fields and the principals of magnetic induction.
A primary reason for the exclusive usage of magnetic fields has been due to poor ability to contain large electric fields, whereas containing a magnetic field has been comparatively easy, due to differences between material properties known as permittivity versus permeability. The ability of a material to carry a magnetic field is characterized by the permeability of free space (μ0), as described by Equation 1 below.
                                          μ            0                    =                                    B              H                        =                          4              ⁢              π              *                              10                                  -                  7                                            ⁢                              H                m                                                    ,                            Equation        ⁢                                  ⁢        1.            
On the other hand, the ability of a material to carry an electric field is characterized by the permittivity of free space (σ0), as described by Equation 2 below.
                                          σ            0                    =                                    D              E                        =                          8.85              *                              10                                  -                  12                                            ⁢                              F                m                                                    ,                            Equation        ⁢                                  ⁢        2.            
The permittivity of free space is over one hundred and forty-one thousand (141,000) times smaller than the permeability of free space. Thus, in order for electric field machines to reach equivalent field densities and/or stress as those of magnetic field machines, and permittivity being an operative material property, it must overcome this substantial material hurdle without failing.
While seemingly simple, the ability to generate and control the positive-negative charges in an electric field machine, sometimes called an electrostatic field when used in machinery, for use in practical machines such as motors and generators has previously been unachievable. However, experimentation with electric field technology has been attempted on numerous occasions, first in 1901 by H. Ho at TIU, again in 1933 by J. Trump at MIT, and more recently in 1971 by O. Jefimenko at WVU.
Previously, this limiting material permittivity property in combination with low dielectric strength, which is a measure of a material's ability to withstand an electric field without breakdown, of a system, has resulted in a poor ability to generate and contain electric fields of sufficient magnitude to be of beneficial use for large power electro-mechanical applications. When attempting to achieve the necessary high electric fields that are required for large power electro-mechanical applications, the low permittivity property in combination with low dielectric strength causes electric field machines to breakdown, which is an unstoppable avalanche arcing process that occurs when the applied electric field strength exceeds the maximum field strength of the surrounding medium, forcing the medium to conduct. Due to one or more of these material limitations that has precluded development for over a century, there is a common belief that large power machinery, on a scale useful for industry, can only be created using magnetic fields.
Prior art researchers of electric field machines may have considered electric field machines based on charge transfer as a way to minimize the electric field containment issue. Electric field charge transfer machines can apply charges to various machine elements via mechanical contacts. Because a mechanical contact transfers a charge of the same polarity to an isolated machine element, the machine element can be repelled from the mechanical contact. A charge transfer type electrostatic machine can include a spark-gap machine, like that considered by Franklin, or the usage of corona to transfer charge. The spark-gap electrostatic machine can use a brush-like contact to transfer a charge to a conductive element. Similarly, the corona electrostatic machine can use a needle or needle-like component to create charged ions that are deposited on an insulating element. In either case, a stationary contact of opposite polarity to the charge depositing contact and positioned some distance away from it, is used to neutralize the charge on the isolated mobile element. However, charge transfer and charge neutralization can create heat and can be inefficient processes. An alternative electric field machine can use a process called electrostatic induction, whereby an external electric field can be used to induce charges in a conductive body to redistribute, in order to create force, torque or energy. An electrostatic induction machine can produce force, torque or energy in relation to the capacitance of the machine.
Using recent advancements in dielectric materials and precision manufacturing, electric field machines, including electrostatic induction machines, that overcome the prior σ0 limitations can now be economically viable. As described herein, when electric field technologies are employed in electric field machinery, such as generators and motors, they can provide numerous benefits, including the efficient and economical generation, transmission, distribution and consumption of HVDC power. Electric field machines can also use lower density materials to lower the machine's weight, they can also use lower cost materials and they can require lower cost processing per unit. These advantages can allow for the economical use of HVDC for shorter transmission distances while still maintaining high efficiency.
The efficiency of magnetic field based machines operating at low speeds or loads can decrease because heating losses (a.k.a I2R losses) occur, even at zero speed such as in a locked rotor condition. In contrast, the efficiency of an electric field machine can not decrease at low speeds or loads because current can primarily occur during charging and discharging of the electric field machine. For this reason, I2R losses of an EFT machine can decrease at low speed or loading. Also, the electric field machine can eliminate the need for back-iron (yoke) that magnetic field machines require, because the divergence of the electric field is not zero, and so it can eliminate core losses and use less material volumetrically.
Further, electric field machines can have higher capacity factor (CF) values than traditional magnetic field machines. For example, an EFT generator with higher efficiency at low speeds can improve the CF of a wind turbine by harnessing more wind energy during low wind speed conditions. FIG. 3 illustrates possible wind turbine efficiency curves of various prior art magnetic systems and an EFT system versus wind speed. Electric field machines can also allow greater versatility for utility scale generators. For example, a large utility power company can use their magnetic induction based generators to meet their base load power needs. Traditionally, deviation in the output power of their base load generators, which is based on magnetic induction, would result in decreased performance and economic value of the generator. A primary reason for this lower value can be due to lower efficiency of the magnetic field induction generator at any operating point other than its rated operating point. In contrast, an EFT generator can not lose economic value if operated at a point lower than its rated value, because its efficiency can increase at lower speeds or loads. This higher economic value may allow utilities to modulate base load production allowing companies to better implement variable energy sources, such as renewable energy sources. FIG. 4 illustrates exemplary efficiency versus percent rated load curves for traditional magnetic field generators and EFT generators.